1. Field of the Invention
The present invention relates to a biometrics authentication system using a microlens array.
2. Description of the Related Art
In recent years, the introduction of personal identification techniques (biometrics) using biometrics authentication into access control in a specific area or bank ATMs has begun. Therefore, an increase in crimes by fake ID cards or identity thefts has become a social issue, so the establishment of a method of personal identification capable of preventing forgery is desired.
As such, a method of identifying a living organism, and methods using faces, fingerprints, voiceprints, irises, veins and the like as authentication data have been proposed. For example, in a system using faces as authentication data, it is difficult to precisely capture characteristics of individuals due to physical conditions or makeup, and the characteristics of faces are easily changed due to growth, so it is difficult to use the same data throughout a lifetime. Therefore, in authentication using faces, it is considered difficult to achieve high precision in general. Moreover, fingerprints, voiceprints, irises and the like are personal information which is relatively less changed; however, forgery such as duplication of a fingerprint through the use of a resin, recording and reproducing of a voiceprint through the use of a recorder, duplication of an iris pattern through the use of a high-definition printer has been perceived as an issue.
On the other hand, the shape pattern of veins under the skin of a finger or a palm hardly changes from approximately two or three years of age, so the shape pattern of the veins can be used as stable authentication data throughout a lifetime. Moreover, it is difficult to visually check veins directly from the skin surface, so it is difficult to forge, and various proposals have been made (for example, refer to Japanese Unexamined Patent Application Publication No. 2006-68328).
Now, in FIG. 14A, an example of a biometrics authentication system in a related art using the above-described vein authentication system is shown. In a technique in the related art, when a finger 2 as an object subjected to authentication is held over a specified position, the vein pattern authentication can be performed. More specifically, when the finger 2 is irradiated with near-infrared radiation by a light source 100 such as an LED (Light Emitting Diode) arranged on the lateral side (or the longitudinal side) of the finger 2, optical absorption of blood hemoglobin flowing through veins can be observed. One refractive converging lens 101 forms an image of veins by such optical absorption on an image pickup device 102 such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and authentication data including a vein shape shown in FIG. 14B can be obtained.
Moreover, to improve the precision (resolution) of authentication data, techniques using a compound eye optical system such as a microlens array using a plurality of microlenses have been proposed (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2003-283932 and 2005-69936). In general, to improve the resolution in a configuration shown in FIG. 14A, it is necessary to increase the numbers of pixels (the sizes of pixels in the case where the pixel pitch is the same) of the converging lens 101 and the image pickup device 102. Therefore, as the converging lens 101, it is necessary to use a lens with a high numeral aperture (NA). However, the lens with a high numeral aperture easily causes aberration, and its manufacturing cost is high, so it is not practical. On the other hand, in the compound eye optical system using a microlens array, a high-precision image can be obtained at low cost by performing image processing on the basis of a plurality of data obtained by the microlenses. Therefore, when a microlens array is used instead of the converging lens 101, the precision of the image data can be improved.